JP2001103795A - Stationary exciting device for synchronous generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an overvoltage from being generated in a field circuit when the field current of a synchronous generator is cut off, to prevent the timing from becoming difficult when a discharge resistor is connected to a field coil by turning on a contact interlocked with the operation of a DC field breaker, to prevent the apparatus from becoming large, and to prevent the cost of the apparatus from increasing. SOLUTION: A thyristor rectifier circuit 4 is connected directly to a field coil 5. A series connection circuit which is composed of a thyristor clover circuit 8 and a discharge resistor 7 is installed in parallel with the field coil. By the cutoff operation of an AC breaker 3 or the rectifier circuit, a rise in the voltage of the field coil is detected, the clover circuit is turned on automatically, and field energy is absorbed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static excitation device used for a synchronous generator, and more particularly to a circuit for rapidly demagnetizing a field circuit.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional static exciting device for a synchronous generator. AC power is taken in from the output of the generator 1 by an exciting transformer 2, and a rectifier circuit (showing a thyristor type) 4 having a semiconductor switch configuration is supplied through an AC circuit breaker 3.
, And supplies an exciting current to the field winding 5 of the generator 1. The firing phase control of the thyristor of the rectifier circuit 4 obtains a gate signal based on the voltage signal of the generator 1.

A DC field breaker 6 provided between the rectifier circuit 4 and the field winding 5 cuts off when the protective relay detects an internal accident of the generator 1 or an accident in the vicinity of the terminal. The field current to the winding 5 is cut off. The auxiliary contactor 6A is formed as an auxiliary contact of the circuit breaker 6 or an electromagnetic switch using the auxiliary contact as a control relay. The discharge resistor 7 absorbs the occurrence of overvoltage in the field winding 5 when the circuit breaker 6 is turned off, and the field circuit is rapidly demagnetized to prevent its dielectric breakdown.

[0004]

The conventional rapid demagnetization circuit is mechanically interlocked by closing the auxiliary contactor 6A just before the main contact of the DC field breaker 6 opens. This interlock needs to be performed at an accurate timing. If the operation timing is shifted, an overvoltage is generated in the field winding and dielectric breakdown is caused.

The conventional interlock is obtained by interlocking mechanical contacts, which complicates the operation timing setting mechanism and its adjustment.

[0006] In addition, DC field circuit breakers are rarely installed or replaced, so that only a small number of rating series are provided by the manufacturer, and there is little room for selection of generators that match the rating of the generator, and they are expensive. Further, the DC field breaker has to always keep spare parts for replacement. Furthermore,
DC field breakers are relatively large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a stationary excitation device which can obtain a reliable interlock operation, and can be reduced in size and cost.

[0008]

According to the present invention, in order to solve the above-mentioned problems, the output of a rectifier circuit is directly supplied to a field winding, and a discharge resistor is connected in parallel to the field winding through a crowbar circuit. The crowbar circuit is automatically turned on when the field voltage rises, and a discharge resistor can be turned on regardless of the field current interruption operation.

In a static exciting device for a synchronous generator for supplying a field current to a field winding of a synchronous generator from a rectifier circuit composed of a semiconductor switch, a series connection circuit of a crowbar circuit composed of a semiconductor switch and a discharge resistor. Is provided in parallel with the field winding, and the crowbar circuit is made conductive when the voltage of the field winding rises due to cutoff of the rectifier circuit or cutoff of a circuit breaker on its AC input side. Features.

[0010]

FIG. 1 is an apparatus configuration diagram showing an embodiment of the present invention. 2 differs from FIG. 2 in that the DC field circuit breaker 6 and the auxiliary contactor 6A are omitted, the thyristor type rectifier circuit 4 is directly connected to the field winding 5, and the discharge resistor 7 is a thyristor type crowbar circuit. 8 in series with the field winding 5
In parallel.

The crowbar circuit 8 is constituted by a thyristor having a bidirectional conduction function that is turned on when the voltage of the field circuit rises. Further, the crowbar circuit 8 can obtain an equivalent function by using another semiconductor element instead of the thyristor as a switch.

The operation of the embodiment will be described. An accident inside the generator 1 or near the terminals is detected by a protective relay, and the AC circuit breaker 3 on the AC input side of the rectifier circuit is cut off (or the thyristor type rectifier circuit 4 is turned off). Due to this trip, the AC circuit breaker 3 and the rectifier circuit 4 are turned off, and the voltage of the field circuit starts to rise.

The crowbar circuit 8 is turned on (the thyristor is turned on) by detecting the voltage rise, and the discharge resistor 7 is supplied to the field circuit. As a result, the energy stored in the field winding is dissipated as heat energy by the discharge resistor 7, and rapid demagnetization is obtained.

Therefore, according to the present embodiment, the ON operation of the crowbar circuit 8 does not interlock with the cutoff operation of the AC circuit breaker 3 and operates by increasing the voltage of the field circuit.
The operation timing is determined by the actual voltage of the field circuit, and the failure of the interlock due to the shift of the operation timing as in the related art is eliminated. Further, the operation circuit and adjustment are simplified as compared with the case where the operation timing is determined by the conventional mechanical interlock.

The circuit configuration may be any as long as a demagnetization current matching the generator rating can be passed through a semiconductor switch such as a thyristor of the crowbar circuit 8, and a design using a number of commercially available elements is used. And eliminate the need for storage management. Further, the crowbar circuit 8 can be constituted by a small semiconductor element, and the size of the device can be reduced.

[0016]

As described above, according to the present invention, the output of the rectifier circuit is directly supplied to the field winding, and a discharge resistor is connected to the field winding in parallel through a crowbar circuit, so that the field current is reduced. Regardless of the shut-off operation, the crowbar circuit is automatically turned on when the field voltage rises, and a discharge resistor can be turned on. This has the effect of achieving cost reduction and cost reduction.

[Brief description of the drawings]

FIG. 1 is a rapid demagnetization circuit showing an embodiment of the present invention.

FIG. 2 shows a rapid demagnetization circuit using a conventional DC circuit breaker.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Synchronous generator 2 ... Exciter transformer 3 ... AC circuit breaker 4 ... Thyristor type rectifier circuit 5 ... Field winding 6 ... DC field circuit breaker 7 ... Discharge resistance 8 ... Clover circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H590 AA01 AA03 AA04 AB01 CC01 CC18 CC24 DD24 DD64 EB02 EB21 FA06 FB05 FC16 FC21 FC25 GA02 HA02 HA03

Claims (1)

[Claims] 1. A static exciter for a synchronous generator for supplying a field current to a field winding of a synchronous generator from a rectifier circuit composed of a semiconductor switch, wherein a crowbar circuit composed of a semiconductor switch and a discharge resistor are connected in series. A connection circuit is provided in parallel with the field winding, and the crowbar circuit is made conductive when the voltage of the field winding rises due to cutoff of the rectifier circuit or cutoff of a circuit breaker on its AC input side. A stationary exciting device for a synchronous generator.